Vaccination is considered to be the most effective and efficient approach to prevent pathogen infection. However, there are still many infectious diseases for which no vaccine is yet available or adequate immunization cannot be achieved. In addition, many vaccines are inadequate because of low efficiency, serious side effects, low stability or high costs. Thus, there is a great need for more effective vaccines and related reagents.
A vaccine contains a pathogen-derived antigenic material, e.g., protein, for inducing protective immune responses. In general, modified proteins, such as lipidated proteins, are more immunogenic than unmodified proteins. Proteins in certain vaccine products have been prepared by expression in E. coli using recombinant technology. However, E. coli is generally viewed as not suitable for producing modified proteins, particularly, lipidated proteins. More specifically, E. coli cells lipidate poorly naturally lipidated proteins and do not produce non-naturally lipidated proteins in lipidated form.